700x40 vs. 27.5 (650b)x48

[TwoWheeledExplorer]

Spec-ing a new bike for touring and gravel. Do a lot a gravel near home for fun and exercise, but am hoping to do more S24O and multi-day self-supported touring since I retired. Open to suggestions as to what would be better for my riding? I used to have an '06 Novara Safari, and to be honest, the only thing I didn't like about it was the 26-inch wheels. Sold it (here) to make way for a 29-er MTB. I realize that I may have just answered my own question, but like I said, I have an open mind.

Ride safe,
Hans

[Pat Lamb]

I can't answer your question, of course, but maybe I can ask some questions to channel your wondering.

Just what did you not like about the 26" wheels?  Was it the width?  Were the tires knobby and stiff?

Where are you planning to ride this bike?  Paved roads, somewhat paved roads, gravel roads, single track?

What's wrong with 700Cx32?  There's surely some reason you're considering alternative standard sized tires.

[RussSeaton]

If your choices are 700C or 650b, then I would definitely recommend 700C wheels.  I cannot understand why this 650b size was brought back from the dead to use on mountain bikes and other bikes.  To sell bikes!!!!  Oh right.  26" mountain bikes were the standard for a long time.  Seemed to work just fine.  Then 29" mountain bikes appeared.  NEW!!!  Maybe possibly they have some advantages over 26".  Maybe.  But 650b???  Midway between the old 26" which were obviously inferior and garbage and the new 29" which are the very bestest greatest thing on earth.  Why would you want half garbage and half wonderful?  700C tires can be found in every tread type from 20mm to 2.9" size.  So tire options for 700C wheels are unlimited.

[Biggus Duckus]

For exactly the reason he said: wider tires.

[RussSeaton]

For exactly the reason he said: wider tires.

700C/29" and 650b/27.5" and 26" tires come in almost all tire sizes from 1 inch or so up to 2 inches or so.  Tire width has almost ZERO to do with choosing 700C or 650b.  You can get about any tire width you want in all tire sizes.  The question asker wants to spec a new bike for touring and gravel.  He lists 700x40mm and 650bx48mm tires in the title for some reason.  700C and 650b tires come in almost every size.  Wider and narrower.  The 650b/27.5" tires seem to be predominantly wider mountain bike sized.  There are only a few tires at the 1.5" width.

[Biggus Duckus]

With 650b you can get wider tires but with the same rolling diameter as thinner 700c tires.  For instance, 650bx48 might have the same "height" as 700x25.  But with a larger contact area than the 25mm tires.

This is good for bikes that have clearance issues on the fork or chainstays due to the roll height, but have some width to spare.  My bike can fit 29x2.1" tires but if I go 650b it can fit 650bx2.3" tires. 

As for the original question.  I think 40 is plenty sufficient for gravel and road.  I like my 700x38s for the same conditions, just make sure you get something sidewall protection and tread or puncture protection.

[TwoWheeledExplorer]

I'm looking at the Schwalbe Marathon Mondials, and 40 mm is widest they come in 700s. The Safari had Conti T&Cs. Great tires, wear like iron, but horrible to take off the rims to patch and I always felt like I had to work harder to cover the same distance. I have Schwalbe Marathon Plus 700x35s on my Volpe.

Hans